Sequence variation in group A Streptococcus pili and association of pilus backbone types with lancefield T serotypes.
BACKGROUND
We previously reported that group A Streptococcus (GAS) pili are the T antigens described by Rebecca Lancefield. We also showed that these pili, constituted by backbone, ancillary 1, and ancillary 2 proteins, confer protection against GAS challenge in a mouse model.


METHODS
We evaluated pilus distribution and conservation by sequencing the subunits of 39 new GAS isolates and used immunoblot analysis and agglutination assays to define the specificity of T sera to pilus subunits.


RESULTS
GAS pili are encoded by 9 different islands within which backbone protein, ancillary protein 1, and ancillary protein 2 cluster in 15, 16, and 5 variants, respectively. Immunoblot and agglutination assays revealed that T type is determined by the backbone variant. This observation enabled us to set up a simple polymerase chain reaction assay to define the T type of GAS isolates.


CONCLUSIONS
We propose the use of a tee gene sequence typing, analogous to the emm gene typing, as a valuable molecular tool that could substitute for the serological T classification of GAS strains. From our sequence analysis and from recent epidemiological data, we estimate that a vaccine comprising a combination of 12 backbone variants would protect against > 90% of currently circulating strains.
Falugi
Fabiana
F
Novartis Vaccines, Siena, Italy.
Zingaretti
Chiara
C
Pinto
Vittoria
V
Mariani
Massimo
M
Amodeo
Laura
L
Manetti
Andrea G O
AG
Capo
Sabrina
S
Musser
James M
JM
Orefici
Graziella
G
Margarit
Immaculada
I
Telford
John L
JL
Grandi
Guido
G
Mora
Marirosa
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005798:Genes, Bacterial; D014644:Genetic Variation; D010802:Phylogeny; D013297:Streptococcus pyogenes / Q000145:classification / Q000235:genetics*
D001426:Bacterial Proteins